The present invention relates to directing a gas flow in a substrate processing chamber.
In the fabrication of semiconductors and displays, materials are formed on a substrate by oxidation, nitridation, ion implantation, chemical vapor deposition (CVD), and physical vapor deposition (PVD) processes. The substrate deposited materials can be also etched to form features, such as interconnect lines, gates and barriers. During such processing, process residues deposit on the internal surfaces of chamber walls and on exposed chamber components. The process residues can include the material being formed or etched, as well as other materials that might result from chemical or physical events occurring during the process. Process residues can also deposit on the surfaces in a non-uniform manner. For example, residues might form in thicker layers near process gas inlets or PVD targets, and may be substantially absent in other areas of the chamber.
The process residues are periodically cleaned from the surfaces of the chamber walls and components. Unchecked build-up of residues can degrade the process being performed in the chamber and reduce substrate yields. For example, residues may flake or crumble from chamber walls during a deposition process and contaminate a layer being formed on the substrate. Also, residues collecting on or around gas inlets and outlets may adversely affect process gas flow rates or composition. Contamination of a substrate or deviation from a proscribed process recipe can lead to the unreliability or inoperability of the device being fabricated on the substrate.
In one cleaning method, residues are cleaned from surfaces in the chamber by a wet-cleaning process in which liquid solvents are applied to chamber surfaces by an operator. Wet-cleaning process are often manually implemented and thus can be slow or ineffective, resulting in extended chamber down-time or incomplete cleaning. For example, different chamber operators may scrub chamber walls with different forces resulting in different levels of cleaning of the chamber between the processing of one batch of substrates and another.
A dry-cleaning process in which an energized cleaning gas is used to etch away residues from the chamber surfaces can also be used to clean the chamber. However, dry-cleaning processes have other problems. For example, surfaces having non-uniform residues may require a prolonged exposure to the cleaning gas to clean regions having thicker residues, resulting in erosion or degradation of chamber surfaces having thinner residues. Chemically resistant or hard-to-clean residues may also require prolonged exposure to a cleaning gas, or the use of highly erosive cleaning gases, which may result in similar problems. Also, highly erosive cleaning gases can also be more toxic or environmentally unsafe.
A further problem with conventional dry-cleaning processes is that the same gas distribution system is typically used for both the process gas and the cleaning gas. Such gas delivery systems generally distribute process gases within the chamber across the substrate surface in a uniform manner to optimize substrate processing characteristics. However, as the optimal distribution of cleaning gas in the chamber can have different requirements than the distribution of process gas, conventional gas distribution systems can fail to provide satisfactory cleaning of residues formed on surfaces inside the chamber.
Thus, there is a need to clean residues from chamber surfaces that may be non-uniformly deposited or chemically resistant to cleaning, without excessive erosion of the chamber surfaces. It is also desirable to be able to distribute the cleaning gas across chamber surfaces to achieve efficient or optimized cleaning of the residues.